Apparatus for reducing the fluid content of a fluid-solid intermixture



Sept. 10, 1946. H. A. TEALE 2,407,303

APPARATUS FOR REDUCING THE FLUID CONTENT OF FLUID-SOLID INTERMIXTURES AFiled Aug. 15, 1943 3 Sheets-Sheet 1 I N V EN TOR. Harald fl. E a/e BY vSept. 10, 1946. TEALE Y 2,407,303

APPARATUS FOR REDUCING THE FLUID CONTENT OF FLUID-SOLID INTERMIXTURESFiled Aug. 13, 1943 I 3 Sheets-Sheeti i0 v M I 65' 1m r j "H mun" i" .iv

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Patented Sept. 10, 1946 APPARATUS FOR REDUCING THE FLUID CONTENT OF AFLUID-SOLID INTERMIX- TUBE Harold A. Teale, Brooklyn, N. Y., assignor toFilter Irvington on Hudson, N. Y., a corporation of New York ApplicationAugust 13, 1943, Serial No. 498,520 4 Claims. (01. 210-188) MediaCorporation,

The invention relates to slurry separators, thickeners, clarifiers orthe like and more particularly to a new and useful apparatus forcontinuously decreasing the fluid content of a solid and fluidintermixture.

Objects and advantages of the invention will be set forth in parthereinafter and in part will be obvious herefrom, or may be learned bypractice with the invention, the same being realized and attained bymeans of the instrumentalities and combinations pointed out in theappended claims.

The invention consists in the novel parts, constructions, arrangements,combinations and improvements herein shown and described.

The accompanying drawings, referred to herein and constituting a parthereof, illustrate one embodiment of the invention, and together withthe description, serve to explain the principles of the invention.

Of the drawings:

Fig. 1 is perspective view of an apparatus embodying the invention;

Fig. 2 is an enlarged fragmentary vertical section, in expandedrelation, of a plurality of typical elements comprising the thickenerapparatus shown in Fig. 1;

Fig. 3 is an enlarged fragmentary section of the elements of Fig. 2 inassembled relation;

Fig. 4 is a fragmentary top plan view of a thickener plate taken on line4--4 of Fig. 2;

Fig. 5 is a fragmentary bottom plan view of a filter plate taken on line55 of Fig. 2; and

' Fig. 6 is a fragmentary vertical section through one element of theassembled apparatus, diagrammatically illustrating the nature of theslurry flow therethrough; and

Fig. '7 is an enlarged perspective view of a section of a plate llshowing the transverse nodes 44' and the transverse valleys 45 on oneside and the longitudinal grooves 25 as Well as their adjacent lands 26;

Fig. 8 is an enlarged partial view similar to Fig. 6 but taken along theline 8-8 in Fig. 7, but with the filter medium 50 in place thereon, andthis figure illustrates what seems to happen to the slurry particles inthe channel 40;

Fig. 9 is a plan view of a portion of a channel 40 and shows a modifiedform of node; and

Fig. 10 is a partial perspective view of the modi fied arrangement ofFig. 9.

The invention is directed to providing novel and useful apparatus forreducing the fluid content of a fluid-solid intermixture (hereinaftercalled a slurry) by virtually continuous filtering or straining actionwherein a clear fluid product is continuously removed from the slurry,thereby continuously increasing the proportion ofsolids remaining in theslurry which may be recirculated or passed several times through theapparatus, as required, to bring about the desired proportion ofsolids-to-fluid therein. The invention is of general application topractically any and all such slurries or intermixtures but isparticularly useful in cases where thickening of the interm'ixture isimpracticable or inefficient by usual means such as settling anddecanting. Hence the invention is applicable to the thickening of manyslurries where solids are very fine or in a state of colloidalsuspension, which cannot be thickened by settling or gravity action.

Many of the novel principles of the invention are broadly and generallyapplicable to the separation or clarification orthickening of fluidscontaining intermixed solids, including gas and solid intermixtures. Inthe succeeding description, however, particular reference will be madeto the treatment of liquid-solid intermixtures and for convenience ofreference the action of the apparatus will be referred to as thickeningand the apparatus itself as a thickener.

The invention employs exceedingly simple and inexpensive-means, but bymeans of novel principles, is enabled to produce very superior resultsin relatively short time and at a low expenditure of power and labor.

The thickening or liquid-removing action of the invention depends uponthe movement of the slurry over or across the surface of a filter medium while under pressure sufiicient to force liquid through saidnledium, maintaining a state of motion in the slurry travelling oversaid medium such that no substantial amount of solid is deposited out ofthe slurry to form as cake on Said medium. In accordance with theinvention the state of motion induced in the slurry to effect thisdesired action is brought about by exceedingly simple stationary meanswithout the interposition of any mechanical agitation or pulsation fromapplied mechanical means or forces. In other words, the required motionand movement of the slurry over the filter medium and the maintenance ofdesired pressures and velocities therein are all effected by static andexceedingly simple devices within the chambers where the filteringaction takes place.

One object of the invention is to prevent the deposition of solidparticles onto the filter medium by maintaining a substantial continuousturbulence throughout the slurry as it travels in relatively highvelocity streams across the surface of the filter medium therebyproducing a substantial scouring action of the liquid against thesurface of the filter cloth or other medium which prevents the formationof any substantial amount of cake or solid matter thereon. The inventionalso provides for recurrently actively forcing or urging the slurryagainst and into contact with the filter medium as it travels thereover,thus providing frequent surges or impulses in the slurry which cause theliquid in same to be driven against and through the medium.

Another principle employed in the invention, either as a concomitant ofthe foregoing or independently thereof, is the maintenance of asubstantially constant velocity in the stream of Slurry passing over alength of filter cloth, This function is preferably efiected by causingthe slurry to travel through channels of decreasing crosssection sothat, as the amount of liquid therein decreases by the filtrationeffect, the loss in volume of the stream of slurry is compensated for bydecrease in the size of the conduit, thereby effectively maintaining agenerally continuous velocity which facilitates the maintenance of theflow of slurry over the filter medium, counteracting the tendency of thesolid particles to settle out on the filter cloth, and, when used incombination with the turbulence-creating means above referred to,enhances the scouring and anti-precipitating action as well,

One feature of the invention which greatly facilitates the successfuloperation thereof is the maintenance of a proper balance of forces andfiuid movements so as to build up and maintain a relatively thin depositor skin of solid matter on the face of the filter medium. This skin ofcake is established at the beginning of the operation and, is maintainedsubstantially constant throughout the continuous recirculation of theslurry through the apparatus. The maintenance of said skin of cake iseffective in providing a clear solid-free liquid product deliveredthrough the filter medium and the force employed are so regulated andbalanced as to prevent the building up of said skin of cake beyond apredetermined very low maximum thickness, yet to establish and maintainsame throughout the operation and in spite of a continuously increasingproportion of solid content in the slurry.

It will be understood that the foregoing general description and thefollowing detailed description as well are exemplary and explanatory butare not restrictive of the invention. Referring now in detail to thepresent preferred embodiment of the invention, illustrated by way ofexample in the accompanying drawings, a general view of an apparatusembodying a preferred form of the invention is shown in Fig. 1. Samecomprises in general a tank 8 for containing the supply of slurry whichis drawn preferably from near the bottom thereof by conduit 2 on theintake side of a motor driven pump 3 and forced thereby through pipe 4past pressure gauge 5 into the top of the thickening unit Ill by meansof inlet pipe 6. The solid-free filtration product of the thickeningunit l0, hereafter conveniently called filtrate, is delivered therefromat one or more points by delivery pipes I5 into a suitable receptaclel6, while the thickened slurry, constituting the mixture which haspassed through the unit Ill, is delivered therefrom by one or moreoutlet pipes l8 which, as shown, feed back into the tank In forre-mixture with the original batch and re-circulation through the unitID as man times as may be required to reduce the slurry to thedesired'liquid-solid ratio. With many products, however, a single passof the slurry through the unit It may be sufficient to bring about thedesired thickener action or on the other hand, the slurry delivered bythe pipe I8 may be passed through a second unit similar to unit I 0 inseries or tandem therewith so that sequential thickening actions on theprogressively thickened slurry may thus be effected,

Referring superficially to the construction of unit Hi, same comprises aplurality of superposed rectangular plate members or elements I l whichare relatively long and narrow and which are mounted to colliectivelyform a rectangular stack of inter-communicating elements or plates oneabove the other, as shown, A bottom supporting plate l2 and an overlyingtop plate l3 are provided, same being somewhat greater in area than theelement plates II, and the entire stack is bound together by a pluralityof vertical rods l'l. pairs of which at either side of the stack aretied by top and bottom cross-members I! and drawn together by nuts l9 atthe threaded ends of the rods. Any other suitable means for compressingor drawing together the several superposed plates or elements of theunit Ill may be provided, it being understood that the hydraulicpressure for the thickening of most products is relatively low comparedwith that used in a typical filter press. Pressures of the order ofabout 15 lbs. per square inch have been used successfully and thereforean expensive and heavy duty clamping or pressure-maintaining means isnot ordinarily required. However, for certain purposes and with somemixtures considerably higher pressures may be used and are sometimesdesirable and in such cases the clamping or pressuremaintaining meansmay be adapted to the higher pressure operations without interferingwith or changing the basic design of the apparatus nor its internalfunctioning.

The detailed construction of the several plates making up the unit l0will be seen in Figs. 2-5.

As shown, th top plate or head stock I3 is provided near one end withthe vertical port 20 for the reception of the inlet pipe 6, the lowerportion of said port being counter-bored at 2|. The port 2ll2l is alinedwith a similar port 22 in the first or head plate 23 of the unit Ill,said head plate being smooth and flush on its top face to match with thebottom surface of the overlying head stock 13. The underface of headplate 23, however, is provided with a plurality of longitudinal grooves25 and lands 26 which serve as channels for the filtrate after same hasfiltered through the filter medium 50 overlying said lands and grooves.As shown, each groove 25 begins adjacent the inlet slurry port 22, andterminates at 28 in a recessed cross-conduit 29. Said crossconduit thuscommunicates with all the discharge ends of the clearate grooves (Fig.5) and in turn communicates with an upwardly inclined central duct 30which directs the filtrate into a discharge channel which, in the headplate, begins with the enlarged socket portion 3| which is alined withsimilar capacity ports in the other plates just below.

The next plate or element II is typical of all those for making up theunit It], except for the head plate 23 and the tail plate 35 hereinafterdescribed. That is, a plurality of said plates ll similar inconstruction thereto, will all be superposed to make up the unit It] andin practice a typical unit may include thirty of such plates combined asshown in Fig. l.

In the preferred construction, as shown, each.

rality of channels or conduits for the travel of the slurry therealongwhile in contact with the filter medium 50 lying against the lands ofthe filter grooves 25 of the plate just above. Preferably, in a unit ofthe general shape and dimensions shown, the plate will be provided withthree parallel channels 40, the inlet ends of which communicate with theslurry port 22 of the plate just above. Each of said channels 40 extendsfrom said inlet end to communicate with a down port 4| near the oppositeend of the plate H so that liquid reaching said end travels downwardlythrough the port M to the next plate below. As will be apparent fromFig. 4 the three channels 4!] of the plate are separated by partitionsor lands 43 which extend parallel for the length of said channels 40.

In accordance with the invention the course of the slurry travellingalong a conduit 40 it continuously disrupted and changed in velocity soas to impart a disrupting turbulence therewithin as the liquid travelsalong said channel. For this purpose the bottom surface of the channelis preferably formed as a wavy surface comprising successive nodes 44and valleys 45 which, as illustrated diagrammatically in Fig. 6, cause aconstant turbulence and scouring activity within the stream of slurryflowing along said channel. The number, depth and spacing of the valleys45 and node 44 do not appear to be especially critical although it isimportant to make frequent changes in the depth of the channel tothereby cause the slurry to be forced upwardly through narrow passagesclose to the overlying filter medium 5!] (Fig. 6) and then to quicklyexpand into zones of greater volume in the valley portions 45.

For example, in plates ll of the general shape shown, having an overalllength of about 5' with grooves All of .8" in length, the approximatelength from node to node is preferably about 4". However, it will beunderstood that the invention is not limited to any particular shape ornumber of elevations or depressions in the slurry guiding channels andthat same may vary with different types of materials, with differenthydraulic pressures and other factors. It will be found by practice withthe invention that certain optimum arrangements of the general designshereinbefore disclosed will obtain with various materials and mixturesof slurries but that a wide latitude may be had in the arrangement andnumber of the elevations and depressions in the grooves withoutdeparting from the essential principles of the invention.

Another feature which has been found helpful in facilitating the desiredcontinuous thickening and prevention of solid precipitation, is theconstruction of the slurry flow channels 49 in such manner that theydecrease in capacity or volume in the direction of flow of the slurrytherealong, thereby to maintain substantially constant the generalvelocity of flow of the slurry in said channels and thus oppose anyslowing down of the slurry flow which in tfirn would promote settlingaction of the solid particles. As shown in Fig. 2, for example, thechannels 4|] in plate I l are of maximum depth at the inflow orrighthand end and taper to a relatively shallow depth at the delivery orleft-hand end thereof.

This feature of narrowing or tapering of the slurry channels has beenfound to be helpful in and by itself in preventing settling out all thesolid material and consequent choking and blinding of the channels. Thesame is true to an even greater extent of the other features of theinvention previously described, i. e. the provision of Wavy surfaces inthe slurry channels to promote turbulence or ripples in said flow. Thatis, each of said features can be used independently of the other andwhen so independently used will improve the thickening action andefficiency of the unit. However, I prefer that they be used together,the combination of the two features contributing to the improvedoperation of the unit. Of the two such features, however, I regard theprovision of the ripple or turbulence-creating elevations anddepressions in the conduit as being more important and, with somematerials, capable of efficient independent use, in which case theslurry channels 40 may be of uniform depth and width (except for thenodes and valleys) throughout their length.

In the preferred construction shown it will be noted that the slurry iscaused to travel through relatively long and narrow passages 48 withreversals of flow direction at the end of each pass. The relativelysharp and. sudden reversals of direction have been found to contributebeneficially to the prevention of solid precipitation, in that saidchanges in direction assist in breaking up the continuity of flow andthe maintenance of turbulence in the streams of slurry. The invention isnot limited to use of relatively long passes of slurry in eachcompartment or section of the unit as, if desired, the pnitmay insteadcomprise a larger number of relatively short sections whereby thereversals of direction of slurry flow occur very frequently and therebycontribute of themselves in a relatively greater extent to theturbulencecreating action desired.

One important feature of the invention is to so regulate the turbulentor rippling flow of the slurry that a relatively thin skin or layer ofsolid matter is formed promptly on the adjacent surface of the filtercloth and thereafter no increase in the thickness thereof takes place.In practice, it has been found that with many substances a skin or cakethickness of about 2;" is the optimum, said skin acting as a filter-aidto increase the clarity of the filtrate while being sufficiently thin asnot to interfere with the prompt passage of liquid through the filtermedium at a relatively high and constant rate. In this connection it hasbeen found that the construction and shape of the nodes 44 is ofimportance in creating a recurrent upward surging of the slurry or itsbombardment against the overhead canopy of filter medium and itsadherent skin of solid particles. That is, the upwardly-directed kineticimpact of the slurry passing over each rise or node in the channelimparts recurrent dashings of the slurry against the filter medium andthereby materially contributes to forcing liquid through the skin andthe filter medium.

Such kinetic impact of particles of the slurry against the filter mediumis illustrated in Fig. 8 of the drawings, wherein the horizontal arrowsat the right hand of the figure indicate the infiowing slurry, while theV-shaped bent arrows indicate a defiective path taken by a slurryparticle as it strikes a rise or node 44 in the channel 40. The A-shapedbent arrows indicate a defiective path taken by a slurry particle as itstrikes the filter medium 50 and bounds away therefrom. The circulararrows indicate eddies and other disturbances created or set-up in theflowing slurry due to these: bounds and rebounds indicated by the bentarrows. This seems to be an explanation of the scouring action of theflowing slurry that keeps down the thickness of the filter cake on thefilter medium 50 from growing thicker than that at which the cakenormally stabilizes itself to the conditions of flow and kinetic impact.

The nodes or elevations 44 in the channels ea may be modified as shownin Fig. 9, which differs from the arrangement of Figs. 4 and 7, forinstance. In those figures, the. crest or ridge of each node extendscontinuously transversely of the channel 40, whereas in the. arrangementof Fig. 9, each general node 44 maybe made up of a plurality ofindividual nodes culminating in crests 44a, Mb, 44c, 44d and so on,respectively, with these crests forming a broken or irregular line moreor less transversely on the channel 40. These irregular crests createfurther scouring eddies or turbulence as indicated by the curved arrowsshown in Fig. 9. Fig. 10 shows how these irregular crests appear.

For most purposes it will be found that wood is a suitable material forconstruction of the units especially because the pressures of operationare ordinarily not high or critical. However, the elements of thethickener unit may be made of molded or laminated Bakelite or othersimilar material, and such plastics are especially effective wherechemicals corrosive to wood, metal or other materials are present, inthe slurry to be thickened. Metal or any other available material may,of course, be used where called for.

The invention in its broader aspects is not limited to the specificmechanisms shown and described but departures may be made therefromwithin the scope of the accompanying claims without departing from theprinciples of the invention and without sacrificing its chiefadvantages.

What I claim is:

1. In a slurry thickener in combination a filter plate having recesseson the lower side, means for removing filtrate from said recesses, afilter medium under said recesses and constituting therewith filtrateconduit means, and a slurry flow directing plate adjacent to theunderside of said 8 filter medium and constituting therewith a conduitfor the flow of slurry therethrough, said conduit having an undulatingbottom surface presenting nodes and valleys for imparting turbulence toa stream of slurry passing through said conduit, and also having outletmeans for passing slurry from said conduit.

2. In a slurry thickener comprising a stack of elements, a plateelement, having on its lower side a downwardly open recess for thereception and flow therethrough of filtrate, a filtrate outlet passage,and having on the upper side a channel for the passage therethrough ofslurry, said channel having an undulating bottom face presenting nodesand valleys, and slurry outlet means at the end of said channel.

In a slurry thickener a stack of plate elements, each plate elementhaving on its lower side a downwardly open recess for the reception offiltrate, and on the upper side a channel for the passage therethroughof slurry, said channel having an undulating bottom face presentingnodes and valleys, a filter medium interposed between adjoining faces ofany two such plate elements, and passage means in said plate elementswhereby slurry passes from the end of a channel in one plate elementinto a corresponding channel of the next lower element and whereby thedirection of flow of the slurry is reversed, a slurry inlet passage forthe: first channel of said stack of plate elements, a slurry outletpassage for the last conduit of said stack of plate elements, and meansfor removing the filtrate from said recesses.

4. A slurry thickener including in combination a filter medium, flowconducting means constituting with the underside of said filter medium aconduit for passing therethrough a stream of slurry along and past saidunderside, said conduit having an undulating bottom surface presentingnodes and valleys for imparting turbulence to said stream passingthrough said conduit, inlet means for passing slurry into said conduit,outlet means for passing thickened slurry from said conduit, and conduitmeans for removing filtrate passing upwardly through said filter medium.

HAROLD A. TEALE.

